In a decision called a ‘blow to the right to know,’ a judge ruled that the final chapter of the CIA’s history of Bay of Pigs won’t be declassified.

A federal judge has ruled that the last volume in a CIA history of the Bay of Pigs invasion that was written more than 30 years ago and 51 years after the ill-fated Cuban mission should remain secret.

In an opinion released Thursday, U.S. District Court Judge Gladys Kessler said Volume V in the CIA’s Official History of the Bay of Pigs was a draft that was “rejected for inclusion in the final publication” and was exempt from disclosure under the Freedom of Information Act.

The Washington-based National Security Archive, a research institute and library, filed suit last year asking for declassification of all five volumes in the set after its previous FOIA requests were unsuccessful.

Volumes I, II, and IV were released last April. Volume III had actually been declassified in 1998 but researchers remained unaware of the fact until a Villanova university professor found it stashed in a box at the National Archives Kennedy Assassination Records Collection in 2005.

The National Security Archive called Kessler’s decision “a regrettable blow to the right-to-know.”

Volume V is a rebuttal by CIA historian Jack Pfeiffer, who died in 1997, of a report by the intelligence agency’s inspector general that found the CIA was primarily responsible for the failure of the invasion.

Who bears responsibility for the failure of the April 14-19, 1961, mission designed to topple the Castro regime has long been debated.

The CIA inspector general’s report concluded faulty intelligence, poor planning, inadequate staffing and failure to inform President John F. Kennedy there was little chance the mission would be successful were to blame. But Pfeiffer put the blame on the Kennedy White House.

The judge agreed with the CIA assertion that release of Volume V would have a chilling effect on current CIA historians who might be reluctant to try out “innovative, unorthodox or unpopular interpretations in a draft manuscript” if they thought it would be made public.

The CIA successfully showed release of Volume V “would harm the deliberative process,” making it exempt from disclosure under FOIA, Kessler said in her opinion.

“The idea that the CIA can advance the cause of accurate historical analysis by hiding history from the peer review of the public is preposterous,” said Peter Kornbluh, director of the National Security Archive’s Cuba Documentation Project.

The National Security Archive had argued that the passage of time should serve as a basis for disclosure of Volume V, but Kessler said the CIA had shown that the passage of time hasn’t “affected the rationale for invoking” the FOIA exemption.

Kornbluh noted an executive order by President Barack Obama that “no information shall remain classified indefinitely” and said the NSA would press the administration to force the CIA to adhere to the order.